Metal Chelate Conjugated Monoclonal Antibodies for Tumor Diagnosis and Therapy

肿瘤相关单克隆抗体（mAb’s）作为恶性肿瘤细胞毒性药物的选择性载体是一种治疗药物。这一假设在动物模型系统中进行了测试，其中单克隆抗体针对与人类疾病相关的抗原。所使用的细胞杀伤剂是粒子发射放射性核素。在适当验证的小鼠肿瘤异种移植模型系统中评估其相对疗效。选择用于研究的放射性核素跨越了放射性核素性质的范围，允许测定发射能量、半衰期和发射类型的影响。目前的研究重点是对α粒子发射放射性核素Pb-212进行广泛的临床前研究，对Bi-213的兴趣减少，并充分激活α粒子发射物At-211的平行研究。正在进行的合作临床试验使用第二代双功能螯合剂1bm - dtpa（又名MX-DTPA或tixetan）来隔离Y-90， Y-90是一种高能纯放射放射性核素，已在临床应用和商业产品Zevalin中得到广泛应用。请注意，使Zevalin （FDA批准的第一种放射性标记抗体治疗药物）成为可能的化学物质是由化学部门开发的。该部门正在进行和计划进行的几乎所有研究现在都使用第三代双功能螯合剂CHX-A“DTPA”来隔离In-111、Y-90、Bi-213和Lu-177。目前已经开始和正在进行的研究继续验证使用Y-86生产的回旋加速器（由化学部门精制和纯化）在PET成像中使用CHX-A“DTPA”。化学部最近报道了许多PET成像研究，关于Y-86用于靶向HER2和HER1（EGFR）的PET成像，用于卵巢癌、结直肠癌、胰腺癌、前列腺癌等多种疾病的可视化；一项未发表的关于Y-86用于靶向HER1（EGFR）的间皮瘤PET成像的研究正在起草中。新型双功能螯合剂和靶向放射治疗的连接剂的临床前评估主要是为了改进偶联化学功能基团的选择和放射性标记的改进。这些改进源于提供用于肽化学的试剂以及适用于放射性镧系元素和α粒子发射放射性核素的特定位点偶联策略。此外，现有双功能螯合剂的新型连接化学已被开发用于肽用途，并与肽合成器仪器一起使用。化学部门的许多已建立的制剂现在正在扩展到肽和其他针对感兴趣受体的小递送载体。同样的新化学和其中的发现经常被认为适合化学科的其他项目。该科创造了一些新的连锁化学剂，用于特定地点的连锁战略，例如弗雷德里克Qasba实验室正在开发的点击化学和特定碳水化合物修饰战略。化学部门的回旋加速器靶处理设备和仪器的验证已经完全启动，这些设备源于该放射性核素生产设施的升级，直接从杜克大学的Zalutsky实验室获得输入。化学部门先前报告了最稳定的at -211连接试剂N-Me-SAPS的验证。最近对该试剂的全面重新合成将促进对其他α排放者进行的平行调查。预期该科最近增加的新人员将加速推动这个项目的这一方面。将Bi-213和Pb-212用于治疗弥散性腹腔内疾病（如卵巢癌或胰腺癌）的高度广泛和集中的临床前研究仍在继续。Bi-213达到了这样一个程度，即成本效益评价加上国家供应不足，实际上迫使终止对这种放射性核素的研究。尽管其疗效显著，但Bi-213在治疗中的全部用途和价值可能永远无法确定。Pb-212的开发继续朝着潜在的临床试验迈进；然而，由于NCI的领导层反应迟钝，计划中的Pb-212试验被转移到UAB。与FDA的ind前会议，确定了GMP生产过程中所需毒性研究的相关问题，同时由工业CRADA合作伙伴完成。为了支持IND的这项治疗卵巢癌的临床试验，Section实验室已经完成了小鼠毒理学实验。除了单独评价放射性核素与特异性单克隆抗体的疗效外，对放射性标记单克隆抗体的联合使用及其与化疗药物的联合使用仍在进行系统的研究。这项调查基于这样一种假设，即单一剂量的靶向放射性核素缺乏癌症治疗的合理基础；联合治疗将显著提高治疗效果。结果表明，单剂量Bi-213或Pb-212结合临床相关抗体，如CC49(Delta)CH2、曲妥珠单抗、西妥昔单抗和现在的帕尼单抗，可以显著增加小鼠模型的中位预期寿命。放射性标记的困难使西妥昔单抗无法进一步研究。使用Pb-212标记的曲妥珠单抗联合吉西他滨显示出令人印象深刻的增强治疗效果；多剂量的Pb-212和吉西他滨联合用药提供了重要的证据，优化药物组合和计划将延长生存期。将Bi-213或Pb-212与紫杉醇联合使用的研究表明，生存期显著延长，且对给药计划有很强的依赖性。同样，与卡铂或顺铂的联合也已进行，并将成为出版物的主题。今年化学组也报道了向肿瘤上的多个分子靶点放射并克服抗原异质性的情况。总之，两种抗体CC49(Delta)CH2和曲妥珠单抗的使用，都是放射性标记的，并以各种排列给药，再次证明了需要经验确定给药顺序，以达到最佳治疗效果，而不是依赖于体外细胞培养研究，因为体外细胞培养研究与体内肿瘤环境没有关系或可预测性。结果显示Pb-212治疗效果优于Bi-213。该科的新人员正在继续与Gius实验室合作开展研究，以调查和确定细胞水平上对高let辐射的损害反应和修复的生物机制以及细胞生物学的遗传调节。Camphausen实验室正在开展评估肿瘤生长环境对基因型影响的研究。此外，正在与Citrin实验室开展研究，以评估目标辐射与外部光束辐射相结合的影响。结合放射性核素成像（SPECT或PET）和近红外染料（光学成像）的三功能显像剂的质量扩展研究纳入了PEG元素。关于染料抗体偶联物的自聚集和信号猝灭特性的重要发现使大量文献受到质疑。这一进展为创建直接定量的光学-放射性核素双模态分子显像剂提供了对基础化学的实际理解。

Tumor associated monoclonal antibodies (mAb's) are therapeutic agents when used as selective carriers of cytotoxic agents to malignancies. This hypothesis is tested in animal model systems with mAbs directed toward antigens associated with human disease. The cytocidal agents employed are particle emitting radionuclides. The relative efficacy is evaluated in the appropriately validated murine tumor xenograft model system. The radionuclides chosen for study span the range of radionuclidic properties available permitting an assay of the effects of emission energy, half-life, and type of emission. Current research focuses on performing extensive pre-clinical studies with the alpha-particle emitting radionuclide Pb-212, with decreased interest in Bi-213, and full activation of parallel studies with the alpha emitter, At-211. Ongoing collaborative clinical trials employ the second generation bifunctional chelating agent 1B4M-DTPA (aka MX-DTPA or tiuxetan) for sequestering Y-90, a high energy pure beta emitting radionuclide well established in clinical applications and in the commercial product, Zevalin. Note that the chemistry that makes Zevalin, the 1st FDA approved radiolabeled antibody therapeutic, possible was developed by the Chemistry Section. Nearly all of those studies ongoing and planned by the Section now employ the 3rd generation bifunctional chelating agent, CHX-A'' DTPA for sequestering In-111, Y-90, Bi-213, and Lu-177. Current studies initiated and ongoing continue to validate use of CHX-A'' DTPA in PET imaging with the cyclotron produced (refined and purified by the Chemistry Section) Y-86. There have been a number of PET imaging studies recently reported by the Chemistry Section regarding the application of Y-86 for PET imaging targeting HER2 and HER1(EGFR) for visualizing a variety of diseases such ovarian, colorectal, pancreatic, prostate cancer; an unpublished study on Y-86 for PET imaging targeting HER1(EGFR) for imaging mesothelioma is in draft. Pre-clinical evaluation of novel bifunctional chelating agents and linkers for targeted radiotherapy with isotopes of interest continues primarily to refine conjugation chemistry functional group options and radiolabeling improvements. These refinements stem from the provision of agents for peptide chemistry as well as for site-specific conjugation strategies amenable for use with both radio-lanthanides and alpha-particle emitting radionuclides. Additionally, novel linking chemistry for extant bifunctional chelating agents has been developed for peptide usage and in use with peptide synthesizer instrumentation. Many of the established agents of the Chemistry Section are now being extended to peptides and other small delivery vectors targeting receptors of interest. This same novel chemistry and the discoveries therein are frequently found to be appropriate to the other project of the Chemistry Section. The Section has created a number of novel linkage chemistry agents for use in site-specific linkage strategies such as click chemistry and specific carbohydrate modification strategies being developed by the Qasba laboratory in Frederick. Studies with At-211 have been fully activated pending validation of the cyclotron target processing facility and instrumentation within the Chemistry Section that has originated from the upgrade in the production facilities for this radionuclide, with input obtained directly from the Zalutsky laboratory at Duke U. The Chemistry section previously reported on validation of the most stable At-211 linker reagent, N-Me-SAPS, and a recent entire re-synthesis of the agent will facilitate a parallel investigation to those ongoing with other alpha emitters. The recent addition of new personnel to the Section is anticipated in spurring this aspect of this project forward at an accelerated pace. The highly extensive and focused pre-clinical investigation into the use of Bi-213 and Pb-212 continues for the treatment of disseminated intraperitoneal disease, e.g., from either ovarian or pancreatic cancer. Bi-213 reached a point whereby evaluation of cost-effectiveness combined with failed national availability effectively forced termination of study of this radionuclide. Despite its significant efficacy, the full range of use and value of Bi-213 for therapy will probably never be defined. Development of Pb-212 continues to move forward towards a potential clinical trial; however, the planned trial with Pb-212 was relocated to UAB due to unresponsive leadership within the NCI. A pre-IND meeting with the FDA that defined relevant issues regarding required toxicity studies while GMP manufacturing was completed by an industrial CRADA partner. Murine toxicology experiments have been completed by the Section labs in support of the IND for this clinical trial to treat ovarian cancer. In addition to evaluation of the efficacy of radionuclides individually with specific mAbs, use of combined radiolabeled mAbs, and their combinations with chemotherapeutics continues to be systematically investigated. This investigation rests on the hypothesis that single doses of a single, targeted radionuclide lacks a rational basis for cancer therapy; combined modality therapies will achieve significant therapeutic enhancements. Results indicate that substantial increases in median life expectancy in murine models are possible with single doses of Bi-213 or Pb-212 conjugated to clinically relevant antibodies such as CC49(Delta)CH2, trastuzumab, cetuximab, and now panitumumab. Radiolabeling difficulties have eliminated cetuximab from further study. Use of Pb-212 labeled trastuzumab in combination with gemcitabine showed impressive enhanced therapeutic efficacy; multi-dosing of both Pb-212 and gemcitabine combined provided significant evidence that optimization of both drug combination and scheduling will extend survival. Studies combining administration of Bi-213 or Pb-212 with paclitaxel demonstrated significant extension of survival with a very strong dependence on administration scheduling. Similarly, combination with carboplatin or cisplatin has also been performed and will be the subject of a publication. The delivery of radiation to multiple molecular targets on tumors and to overcome antigen heterogeneity was also reported this year by the Chemistry Section. In sum, the use of two antibodies, CC49(Delta)CH2 and trastuzumab, both radiolabeled and administered in a variety of permutations demonstrated again the requirement for empirical determination of administration order to achieve optimal therapeutic efficacy as opposed to the reliance on in vitro cell culture studies that pose no relationship or predictability to in vivo tumor environments. Results have indicated superiority in therapeutic response to Pb-212 over Bi-213. Studies initiated in collaboration with the Gius lab to investigate and define the biological mechanisms at the cellular level of both damage response and repair as well as genetic regulation of the cell biology in response to high-LET radiation are being continued by new personnel in the Section. Studies with the Camphausen lab to evaluate the impact of tumor growth environment on genotype are being initiated. Additionally, studies with the Citrin lab are being initiated to assess impact of targeted radiation combined with external beam radiation. Studies to expand the qualities of trifunctional imaging agents combining radionuclidic imaging (SPECT or PET) and NIR dye (Optical imaging) incorporated an element of PEG. Critical discoveries were made regarding self-aggregation and signal quenching properties of dye-antibody conjugates puting a significant body of literature in doubt. This advance provides actual understanding of the fundamental chemistry for the creation of directly quantitative Optical-radionuclidic dual modality molecular imaging agents.